Direct Inhibitory Effect of Estrogen on Leydig Cell Function of Hypophysectomized Rats

The effects of estrogen upon testicular gonadotropin receptors and Leydig cell responses were studied. Immature hypophysectomized rats were treated for 7 days with 50 μg FSH, with or without diethylstilbestrol (DES). Daily injections of FSH induced a marked increase in testis weight; this weight increase was inhibited by concomitant DES treatment. FSH also induced an increase in testicular LH/hCG receptor content; the increase in [125I]iodo-hCG binding was not affected by daily injections of low doses (0.01 and 0.2 μg) of DES but was prevented by treatment with high doses (5 and 20 μg) of DES. In contrast, no significant change in testicular [125I]iodo-FSH-binding capacity was detected in any treatment group. Functional responses of the Leydig cells of hypophysectomized rats were studied by incubation of decapsulated testes with or without a saturating concentration of hCG. Daily treatment of FSH caused a marked increase in both basal and stimulated levels of testosterone production. In contrast, with or ...